1. Field of the Invention
The invention relates to wheelchairs, and in particular to the attachment of a seat to a chassis of a wheelchair. More particularly, the invention relates to an articulating attachment of a seat to a chassis of a wheelchair which provides for improved shock absorption, control and stability of the wheelchair.
2. Background Art
As a result of continuing population growth and improved longevity for people around the world, it follows that wheelchairs will be an increasingly integral part of society. When selecting a wheelchair, a user can consider choices ranging from very simple and inexpensive models to very complex and expensive units. As a general rule, the more feature-laden and complex a wheelchair is, the higher its cost, and thus many consumers are unable to afford features which they find desirable in a wheelchair. Therefore, one goal of many wheelchair manufacturers is to provide as many features as possible in a reliable wheelchair for the lowest possible cost.
One such feature which can add significant cost to a wheelchair is a suspension system. A suspension system, similar to that which can be found on other types of wheeled vehicles such as cars and trucks, is incorporated in a vehicle for several reasons. One reason is to absorb shocks and thereby insulate from shocks the people and/or cargo being carried by the vehicle. For example, during use of a wheelchair, small bumps or depressions on the surface on which the wheelchair is traveling can cause such shocks. Another common objective of a vehicle suspension is to maintain all of the wheels of the vehicle on the ground when such relatively small bumps or depressions are encountered, to maintain steering control and stability of the vehicle.
Such shock absorption, control and stability can be achieved in wheelchairs having sling-type seats integrated on an articulating crossbrace-type chassis, since the non-rigid nature of the sling seat facilitates articulation of that type of flexible chassis. More specifically, when one of the wheels of the wheelchair travels over a bump or a depression, the generally vertical articulation of the chassis and seat effectively absorbs the shocks caused by the irregularities in the travel surface. This articulation also maintains all of the wheels of the wheelchair in constant contact with the travel surface for reliable steering control and stability of the wheelchair. It should be noted that such articulation typically only occurs when a single wheel encounters a bump or a depression, and usually fails to occur when more than one wheel encounters such an obstacle. Moreover, such articulation is only effective in absorbing shocks and maintaining control if the bumps or depressions are relatively small.
However, many wheelchairs having crossbrace frames, which also are useful for storage and transport of the wheelchair since a crossbrace chassis folds into a compact profile, utilize upholstered captain or van-type seats which provide increased comfort for the occupant of the wheelchair. Captain or van-type seats also are considered more aesthetically pleasing than sling-type seats to many wheelchair users. Unfortunately, a drawback of such seats is that they have a rigid structure which prevents any articulation of the crossbrace-type chassis. Thus, a need exists in the art to provide an economical alternative to suspension systems for shock absorption, control and stability of crossbrace-type chassis wheelchairs having rigid van seats mounted thereon.
The present invention economically solves many of the problems of stability, control and shock absorption for wheelchairs having a crossbrace chassis with a rigid van-type seat mounted thereon, by making a simple, inexpensive and yet effective structural change which in turn changes the manner of attachment of the van seat to the chassis. More particularly, such a structural change enables articulation of the chassis relative to the seat at the interface of the chassis and seat in certain instances, when bumps, depressions or other irregularities in the travel surface of the wheelchair are encountered. Such articulation protects the occupant from shock and maintains occupant control and wheelchair stability on the travel surface.